The owner of the N52 series engine got in touch with me.
The engine has lost power. Obviously, something happened…
The reading of the error messages indicated only the error message regarding CO catalytic converters.

The fuel mixture was correct, the load to the engine – low, and… The tests of the catalytic converters (regularly) failed. Yes, if the DME error message memory has the error messages regarding catalytic converters recorded, the engine’s power is limited. It goes without saying.
From live data:

Readings of the control probes indicate the oxygen in the exhaust all the time.

Problems with the control probes themselves?
Nernst resistance – correct. Test results of the Lambda probes:

As we see – everything is OK with the probes. Air suction in the exhaust? No, that, too, was checked.
Incorrect individual fuel mixture in cylinders, misfires?

Yes, the mechanical efficiency of cylinders No.1 and No.3 is increased. But, the most important – the flywheel is not adapted! How so?

The vehicle owner admitted – yes, he had deleted the adaptations. And that he was not aware that the new ones should be created.
After the correct creation of new adaptations:

As we see, the flywheel is adapted now. But the most important – the mechanical efficiency of all cylinders is correct now! The vibration of the engine – disappeared!
Conslusion: the engine has no problem with VVT (and HVA); it has no problem with leaking of the injectors (at least for a warm engine). Everything looks great!
I received a video with Rough run. No misfires were identified; the owner of the vehicles does not complain regarding the shivering of the engine.

But now, in addition to the error message regarding catalytic converters, such ones have appeared:

These are the error messages regarding both wideband probes. Although their heating is forced, they have not reached the correct mechanical efficiency.
Should admit – not a popular defect. Original probes usually don’t have such problems.
No, the probes are not replaced; the car has been used for 10 years. Previously, no such problems have been observed.
Still – the error messages regarding the catalytic converter are recorded on a regular basis, and readings of the control probes confirm the oxygen after the catalytic converters.
Here Testo graphic (on the left – control probes, on the right – readings of the wideband probes):

All data indicate that the efficiency of the catalytic converters is really coming to 0! The car’s mileage is only 200.000 km, so natural wear won’t be the culprit.

What can cause such troubles with catalytic converters and probes? The only option, which I can imagine – fuel additives. I asked the question to the owner of the vehicle, and the answer did not surprise me: yes, recently, he had experimented with Liqui Molly additive for cleaning the injectors and catalytic converters.
Congratulations to the vehicle owner – his experiment confirms that such additives can not be used. In the next stage – both catalytic converters and probes should be replaced.
Remember – you CAN NOT use any additives for modern engines! Even if the most harmless “upgraders” and “cleaners” can cause big headaches and impressive expenses!